This application claims priority to Australian Application No. PQ9331, filed Aug. 10, 2000.
The present invention relates to an apparatus for achieving weld build up. More particularly, the present invention provides an apparatus for achieving weld build up on the surface of a bore.
Many pieces of apparatus include one or more bores. Such bores may receive shafts or pins to thereby connect other apparatus via the bore. For example, earthmoving excavators have various buckets or blades attached thereto via pins that pass through bores formed in eyelet extensions connected to the buckets or blades.
With use, bores can become worn and lose their required dimensional tolerance. In the example of buckets and blades used on earthmoving equipment, this causes clearance and subsequent loose fit; which is unacceptable. To restore worn bores, it is common to apply a layer of weld metal to the bore. This layer of weld metal is then machined to attain a smooth finish and the required dimensions within the bore.
In order to improve the quality of weld build up in bores, automated bore welding equipment has been developed Such bore welding equipment typically comprises a welding head mounted to the end of a rotatable shaft. The rotatable shaft is rotated by a drive means. An axial drive means moves the rotatable head along the axial extent of the bore. The axial drive means may operate continuously, in which case a helical bead of weld metal is deposited in the bore. Alternatively, the axial drive means may operate only when a full diameter of weld metal is deposited in the bore such that adjacent diameters of weld metal are deposited in the bore.
An example of a bore welding apparatus is described in U.S. Pat. Nos. 4 687 899 and U.S. Pat. No. 4 873 419, both in the name of Acheson. The bore welding apparatus described in these patents comprises a hollow, rotatable drive spindle that carries an electrical welding torch at one end thereof. The welding torch terminates in a nozzle. The drive spindle is arranged to feed electrical current, welding wire and protective gas to the welding torch.
In order to provide rotating rotating to the drive spindle whilst allowing the electrical current, welding wire and protective gas to be supplied to the welding torch, the apparatus is provided with a power coupling that has a first housing and a second housing. The first housing is connected to the drive spindle and rotates with the drive spindle. The second housing is fixed against rotation by a torque resistant means. A first washer is soldered to the first housing and a second washer is soldered to the second housing. A spring and thrust bearing arrangement forces the housings toward each other and keeps the first washer in contact with the second washer The second housing is also slipped over a stem of the first housing. Axial movement of the welding torch is achieved by a rack and pinion type arrangement in which a rack on a quill is driven by a pinion wheel that rotates under the action of a worm gear driven by a worm rod. The worm rod is rotated by a separate drive motor.
The welding apparatus is mounted to a cantilever-type mounting arrangement. This mounting arrangement can be attached to the work piece by a magnetic head or by mechanical clamping means. In practice, it has been found that it is difficult to accurately align and maintain the position of the bore welding apparatus using that mounting arrangement.
Another bore welding apparatus is described in Australian patent no 717802 in the name of Russo. The apparatus described in this patent can perform the boring of holes or the surfacing of welding in holes. The apparatus comprises an external hollow shaft (called the xe2x80x9ccool carrying shaftxe2x80x9d). When used as a bore welding machine, a welding torch is carried on the end of the shaft. The tool carrying shaft has a projecting key along its length and this key engages with a key way formed inside a tubular motor hub that is located at the forward end of a tubular box. The tubular motor hub has a ring gear mounted on its external surface and this ring gear engages with the gear mechanism of an electric motor to thereby cause rotation of the motor hub As the tool carrying shaft is keyed to the motor hub, the tool carrying shaft also rotates with the motor hub.
The bore welding machine also includes a further electric motor that drives a gear that engages with a rack formed on an external shaft. This external shaft is coupled by two internal shafts to the tool carrying shaft. The rack and gear mechanism is used to cause longitudinal movement of the external shaft, and hence longitudinal movement of the tool carrying shaft with respect to the bore being repaired.
When used as a welding machine, the machine is mounted to the work piece. An auxiliary shaft is required to be mounted to the work pieces which auxiliary shaft hooks to the tool carrying shaft to thereby center the tool carrying shaft. The mounting arrangement of the machine described in Australian patent number 717802 fixes the position of the motor hub with respect to the work piece. Consequently, the tool carrying shaft must have the key that engages with the key way in the motor hub to enable the tool carrying shaft to move longitudinally through the motor hub during axial movement of the tool carrying shaft.
In a first aspect, the present invention provides an apparatus for achieving build up of a weld metal inside a bore comprising a torch tube carrying a welding torch, said welding torch being positioned intermediate the ends of the torch tube, said torch tube being adapted to be mounted to a work piece by mounting means, rotating drive means for rotating the torch tube and axial positioning means for moving the torch tube in an axial direction relative to the bore.
As used through out this specification, the term xe2x80x9crotating drive meansxe2x80x9d is used to refer to a drive means that causes rotation of the torch tubes.
In an embodiment of the present invention, the torch tube is connected to a coupler means, said coupler means having a fixed portion and a rotatable portion. The coupler means provides a suitable coupler for coupling a welding apparatus to the torch tube. The coupler means may have a welding apparatus connection on the fixed portion thereof for connecting to a welding apparatus, such as a conventional MIG welding apparatus. The coupler means and the torch tube provide a suitable assembly for conveying electrical current, welding wire and/or protective gas to the welding torch.
The apparatus of the present invention preferably further comprises fixing means for selectively fixing the relative axial position of the torch tube in the apparatus. The fixing means may be selectively operable between a fixed position in which the relative axial position of the torch tube is fixed and a disengaged position in which the relative axial position of the torch tube in the apparatus can be altered. The fixing means most preferably can be selectively connected to and disconnected from the torch tube. The fixing means suitably comprises clamping means for clamping onto the torch tube.
The apparatus may further comprise connecting means for operably connecting the rotating drive means to the torch tube.
The connecting means may connect the rotatable portion of the coupler means to rotating drive means. However, the connecting means used in the present invention most suitably connects the rotating drive means to the torch tube by a pulley and drive belt arrangement or by a geared arrangement.
The rotating drive means may suitably comprise a drive motor that causes rotation of a first gear or pulley, said rotation of the first gear or pulley causing rotation of a second gear or pulley to thereby cause rotation of the torch tube. Preferably, the second gear or pulley is mounted to or formed on the fixing means to thereby cause rotation of the fixing means when the fixing means is connected to the torch tube. More preferably, the fixing means comprises a hub, such as a split hub, and the second gear or pulley is mounted to or formed on the hub to thereby cause rotation of the hub when the hub is connected to the torch tube.
The axial positioning means used in the present invention preferably comprises an axial positioning member in use having one end in contact with the work piece being worked upon and longitudinal position moving means for causing relative longitudinal movement of the axial positioning member. The axial positioning members preferably comprises a screw means that passes through at least one nut mounted on or in the apparatus and the longitudinal position moving means comprises a drive motor for causing rotation of the screw means. The axial positioning means may alternatively have a free end in contact with another piece arranged in fixed relationship with the work piece.
Throughout this specification, the term xe2x80x9cscrew meansxe2x80x9d or xe2x80x9cfeed screwxe2x80x9d includes a bar or similar elongate member having an external thread formed thereon. The screw means or feed screw does not need to be a tapered member, nor does it require a screw head to be included.
Rotation of the screw means causes the screw means to be moved longitudinally or axially by interaction of the rotating screw means with the at least one nut. As one end of the screw means is in contact with the work piece, axial movement of the screw means causes the apparatus to move axially with respect to the work piece. Alternatively, the longitudinal position moving means comprises a drive means for rotating the nut which will, in turn, cause the screw means to extend through the nut. In another embodiment, the axial positioning means comprises a shaft that can move longitudinally by interaction with a rack gear. In a further embodiment, the screw means may pass though a threaded member, such as a threaded hub, whereby relative rotation of the screw means and the threaded member causes relative longitudinal movement between the threaded member and the screw means.
A similar mode of action may be utilized in embodiments that employ a different axial positioning member and longitudinal position moving means. One example would be a shaft that is longitudinally moved by rollers.
In preferred embodiments of the present invention, the torch tube is mounted to the work piece by mounting means that contact the torch tube at two locations. This allows for the torch tube to be securely held in the desired position. The torch tube is preferably maintained to the work piece by mounting means that comprise align bore bearings located on opposite sides of the bore or opposite sides of the work piece. The torch tube can rotate in the mounting means and also move or Slide through the mounting means in an axial direction.
In all aspects of the present invention, the torch tube need not be a cylindrical tube. Indeed, the torch tube may have any external shape, the basic requirement for the torch tube being that it is elongate with a passage therein.
In an especially preferred embodiment of the present invention, the apparatus comprises a housing for housing the rotating drive means and the longitudinal position moving means. The housing may also comprise a passage through which the torch tube can extend.
In a second aspect, the present invention provides an apparatus for achieving build up of weld metal in a bore of a work piece, the apparatus comprising a torch tube carrying a welding torch, rotating drive means for rotating the torch tube, axial positioning means for controlling axial positioning of the torch tube relative to the bore and connecting means connecting the rotating drive means to the torch tube, said connecting means being selectively operable to connect to the torch tube wherein the relative axial position of the rotating drive means and the torch tube is fixed and to be disconnected wherein the relative longitudinal position of the rotating drive means and the torch tube can be altered.
In a third embodiment, the present invention provides au apparatus for achieving build up of weld metal in a bore of a work piece, the apparatus comprising a torch tube carrying a welding torch, rotating drive means for rotating the torch tube, and axial positioning means for controlling the axial position of the torch tube relative to the bore, wherein the axial positioning means comprises an axial positioning member having an end in contact with the work piece and axial position moving means for causing relative axial movement of the axial positioning member to thereby cause axial movement of the torch tube relative to the bore.
In this aspect, the axial position moving means causes relative movement between itself and the axial positioning member.
In a fourth embodiment, the present invention provides an apparatus for achieving build up of weld metal in a bore of a work piece, the apparatus comprising a torch tube carrying a welding torch, rotating drive means for rotating the torch tube, axial positioning means for controlling axial positioning of the torch tube relative to the bore and fixing means for fixing an axial position of the torch tube relative to the apparatus, said fixing means being selectively operable to connect to the torch tube, wherein the relative axial position of the torch tube is fixed and to be disconnected wherein the relative longitudinal position of the torch tube can be altered.
Preferred embodiments of the various features of the second and third aspects of the present invention are as described with reference to the preferred embodiment of the first aspect of the present invention.
A detailed description of preferred embodiments of the present invention will now be given with reference to the accompanying drawings. It will be appreciated that the drawings are intended to illustrate the present invention and that the invention should not be considered to be limited to the embodiments shown in the drawings.